Education Technology

Isosceles Triangle

Published on 06/09/2008

Activity Overview

In this activity, students construct isosceles and equilateral triangles. They discover that if two sides of a triangle are congruent, then the angles opposite them are congruent. They understand that an equilateral triangle is also equiangular.

Before the Activity

Install the Cabri™: Jr. App on the students' graphing calculators using one of these two methods:

  • TI-Connect™,  a TI Connectivity Cable, and the Unit-to-Unit Link Cable
  • TI-Navigator™  "send to class" feature
  • See the attached PDF file for detailed instructions for this activity
  • Print pages 15 - 16 from the attached PDF file for your class
  • During the Activity

    Distribute the pages to the class.

    Follow the Activity procedures:

  • Construct an isosceles triangle
  • Measure and label segments and angles of the triangle
  • Identify the sides and angles that are congruent
  • Verify this relationship with different isosceles triangles
  • Observe that if two sides of a triangle are congruent, then the angles opposite them are congruent
  • Create an equilateral triangle using the Regular Polygon feature
  • Measure the angles
  • Observe that if all sides of a triangle are equal, then the triangle is equiangular
  • Alter the triangle and verify if the relationship holds true for all equilateral triangles
  • After the Activity

    Review student results:

  • As a class, discuss questions that appeared to be more challenging
  • Re-teach concepts as necessary